The concentration of potassium is higher in red blood cells than in the surrounding blood plasma. this higher concentration is maintained by the process of: ) circulation
(2) diffusion
(3) excretion
(4) active transport

Option 4, active transport

Explanation:

In active transportation, external force is used to move any substance against the concentration gradient. .This active transportation leads to movement of potassium in into the cell where the concentration of potassium ion is already high. While the sodium starts moving out of the cell. The energy for active transport is provided by the ATP. When the level of ATP reduce, the red blood cells attain spherical shape as the water and sodium move into RBCs.

Hence, option 4 is correct

c. earths continental crust is thicker than its lithosphere.

because, the lithosphere is the outermost layer of the earth/ 100 km thick and is defined by its machanical properties.the lithosphere contains oceanic and continental crust that varies in age and thickness across locations and geologic time. the lithosphere is the coolest layer of the earth in terms of temperature. the term lithosphere should not be confused with the use of "geosphere" which is used to indicate all of earth systems, including the atmosphere, hydrosphere   and biosphere. the surface of the earth can be divided into the continental crust and the oceanic crust.   the continental crust is made mostly of granite while the oceanic crust is made of basalt. the average thickness of the continental crust is 25 miles and the average thickness of the oceanic crust is 5 miles.   three types of rock, igneous, sedimentary, and metamorphic, make up the surface of the earth. that's why 3 option is preferable.

bacterium is not correct